Urban planners predicted that Millennials would prefer renting apartments in dense cities over owning homes in low-density suburbs. So they told regional governments to restrict low-density development and promote high-density housing instead. Now, Millennials are 18 percent less likely to own homes than their parents did when their parents were young: in 1990, 45 percent of 25-34-year-olds owned their own homes; by 2015, it was just 37 percent.

Were urban planners correct? No, says a report from the Urban Land Institute. Instead, Millennials just prefer to live in expensive cities, and that has depressed their homeownership rates.

I don’t think the report is quite right. According to the American Community Survey’s table S0101, which breaks down population by age groups, Millennials are a little more attracted to large urban areas than others, but the difference isn’t enough to account for an 18 percent decline in homeownership rates. The data show that 13.7 percent of Americans are Millennials (which the Urban Institute defined as ages 25 to 34 in 2015), while Millennials make up 15.1 percent of urban areas of 1 million people or more. That’s a significant difference, but certainly not enough to reduce homeownership by 18 percent by itself.

The real problem is that urban planners convinced cities to apply their prescription to nearly half the housing in America. Combining American Community Survey tables B19113 (median family income), B25007 (median home prices), and B25003 (occupied homes) on a county level, the median value of about 45 percent of American housing is more than three times median family incomes. With few exceptions, prices rise above three times incomes only when government policies make it difficult for homebuilders to meet demand.

For example, in 1969 the only places in America where housing cost more than three times incomes were Hawaii and Stamford, Connecticut. I don’t know why Stamford was on the list, but Hawaii had passed legislation strictly regulating where people could build homes in 1961. Other states and urban areas didn’t do so until the 1970s, and as they did so their housing prices rose faster than incomes as well.

Thanks to the urban planning prescriptions, housing is prohibitively expensive in too many areas. While median home prices are more than three times median family incomes in 45 percent of housing, it is more than four times in 24 percent of housing and more than five times in 14 percent of housing.

Millennial homeownership rates are greater than 45 percent in Idaho, Indiana, Iowa, Maine, Michigan, Minnesota, Nebraska, New Hampshire, North Dakota, South Dakota, Utah, West Virginia, and Wyoming. These are all affordable states that have made little attempt to regulate rural development. Millennial homeownership rates are below 30 percent in California, DC, Hawaii, and New York. California and Hawaii have the strongest growth management laws in the nation and DC and New York City are hemmed in by growth-managed states and counties in Maryland, Virginia, Connecticut, and New Jersey. Millennial homeownership rates are also depressed in Florida, Massachusetts, New Jersey, Oregon, and Washington, each of which have their own forms of growth management.

While Millennials are slightly more attracted to big urban areas with expensive housing, Millennial homeownership rates would be well below those of previous generations even if no such attraction existed. This is simply because so much housing has been made artificially expensive.